>That is pretty clever but how did they manage to do that exactly?
Lots of experience:
Phone Bomb Kills Terrorist Yahya Ayyash
January 5, 1996
Hamas bomb maker Yahya Ayyash is killed in Gaza City when his cellphone explodes during his weekly phone call to his father in the West Bank. It is a targeted assassination by the Shin Bet, Israel’s internal security service, which intercepts the call, confirms Ayyash’s identity and detonates the explosives, instantly killing him.
Ayyash, one of the founders of Hamas’ Izzadin Kassam Martyrs Brigades, designed many of the bombs used in a wave of Palestinian suicide attacks on Israelis during the 1990s. Ayyash, who had a degree in electrical engineering and was nicknamed “The Engineer,” joined a wing of Hamas in 1992. He created bombs that killed more than 80 Israelis and maimed 400 others.
After learning in 1995 that Ayyash had secretly moved from the West Bank to Gaza, Israeli intelligence eventually found him among Hamas insiders in Gaza City. The Shin Bet determined that an arrest raid or airstrike would fail or would lead to unnecessary civilian casualties. A Hamas informant who reportedly received $1 million and refuge in the United States helped the Shin Bet smuggle Ayyash’s phone out of and back into Gaza so it could be turned into a bomb.
https://israeled.org/phone-bomb-kills-terrorist-yahya-ayyash/
Exploding phone kills car-bomber
The man most wanted by Israel, a Palestinian known as "The Engineer," was killed Friday in the Gaza Strip, apparently by a booby-trapped cellular phone that blew up near his right ear.
He is widely believed to be the man who made suicide bombings a terror weapon against Israel in recent years.
There was no public confirmation of the death either from Israel or from the Palestinian Authority, but officials on both sides privately confirmed it. So did Hamas, the Islamic opposition movement in whose name "The Engineer," Yahya Ayyash, operated.
https://www.tampabay.com/archive/1996/01/06/exploding-phone-kills-car-bomber/